not at all, we did brents car way back i thik when we sold cammtech cams (great cams too btw) and i spent hours getting the cam timing to the point it lost very little.... BUT i can tell you now if i do one run with it on and one run off on the dyno the differrence can be huge. (more power and torque).. just ask tao, we have is car in every fortnight and one night were chasing a 500rpm lag issue between tunes and it turned out the vtc plug had vibrated off.
Every tune we do that has vtc get a run with it off and run with on constantly (but not a full pull to redline when on constantly) the intersection point is easily discernable.... in power and torque terms that is.